The present invention relates essentially to a coupling for optically connecting a light-conducting element and an electro-optical element. Such optical couplings may, for example, be used to optically connect optical fibers with a light-emitting diode, photodiode or phototransistor.
Commercial light conductors consist of a bundle of very fine optical fibers, made of glass or quartz and the like. The fiber bundle is surrounded by an enveloping tube. A socket with a terminal opening is pushed and fastened over each end of the tube. The ends of the individual fibers exit at the terminal openings, and are face ground there. In order to optically couple an electro-optical element to an end of the light conductor, a suitable coupling element may be provided with a bore, having a diameter which corresponds with the diameter of the socket at the end of the light conductor. An electro-optical element can then be introduced from one side of the coupling element and the light conductor can be pushed into the coupling element from the opposite side. The diameter of the sockets of the light conductor corresponds to the diameter of the housing of the electro-optical element, which is usually mounted in a TO18 or TO46 housing. Such housings are commonly used for transistors, and supplied with a transparent end surface which is usually a glass disk or a focusing lens. The distance between the electro-optical element and the end of the light conductor can be adjusted by pushing the light conductor back and forth in the coupling element, so as to achieve optimum focusing and maxium light-transmitting efficiency. The distance can then be set by fixing the light conductor in the coupling element with setscrews or a permanent adhesive bond.
Heretofore, coaxial connectors also have been used as optical couplings, the end of a light conductor being glued into a plug of the coaxial connector. A matching socket, which is sold commercially with the plug as part of the coaxial connector, comes with built-in insulating inserts and contact elements. Thus, the socket must be modified to make it suitable for use with the plug having the light conductor therein. For this purpose, the contact elements are usually removed from the socket and the insulating inserts are bored out to the diameter of the housing of the electro-optical element. The electro-optical element, for example a light-emitting diode, a photodiode or a phototransistor, is then inserted into the socket and firmly glued in place. One disadvantage of these prior art optical couplings is that the electro-optical element cannot be replaced, in case of a deflect of different experimental purpose, without replacing the entire socket.